AN'KNDIX 285 The preparation of potassium iodide-starch paper is made by clipping strips of filter paper into a thin solution of starch paste to which a little potassium iodide has been added, and drying the paper. The oxidation of a side-chain by means of permanganate solution is one which is commonly employed where the acid is required. The monohalogen derivatives are readily oxidised in this way, but greater difficulty is experienced if two halogen atoms or other acid groups are present. The dichlorotoluenes, for example, are only slowly attacked. I'RKI'ARATION 67. lodOBOtoluene. The most interesting of the compounds belonging to this group, which were carefully investigated by V. Meyer, is the substance prepared by shaking a mixture of iodosoben/ene and iodoxyben/.ene (obtained by the oxidation of the iodoso-compound) with moist silver oxide. Diphcnyl- iodonium oxide is thus produced, which in basic properties resembles ammonium hydrate, c,;ii:,in j <Y,n,,i<>:. i Agon (r(;ii;,u.oii i- Agio.,. With hydriodic acid it forms the iodide, (C(iII,-).J.I. I'UK PA RATION 6<> Diazoaminobonzeiie. Dia/oamino-compounds are also formed by the action of dia/.onium salts on primary and secondary amines of both the aliphatic and aromatic series. The method given in the preparation must then be modified. The dia/.onium salt is first prepared, and the amine stirred in with the addition of sodium acetate. The sodium combines with the mineral acid, liberating the weaker acetic acid, which thereby assists the separation of the tlia/.oainino-compound. Compounds of the following formula; have been prepared in this way. (',;II ,N:N.C,}n I.CH.. I)iuy.c>l>Lmeno-:imiiioloUtenc < %t;l I;,N:N. NHC.,1 I;, I)i:t/,obcn/.c»c-cthyl:iminc. < Y,I I;,N:N.N(C! i:,)o Diaxoben/cne-dimethyUimme, I )ia/.obenzene-pipcridine.